1. Field of the Invention
The present invention relates to a process for producing pellets having straight cut surfaces and a uniform cut length by cutting strands.
2. Description of the Prior Art
A strand cutter comprising feed rolls, a fixed blade and a rotary blade is generally used for cutting strand-shaped articles, which are obtained by melt extruding a thermoplastic resin or extruding a solution thereof through a die plate into a liquid, into pellets having a length of 1.0 to 5.0 mm. The cutter adequately cuts strands having a degree of hardness or rigidity, but it does not cut soft and flexible strands into pellets having no obliquely cut surfaces and a uniform cut length.
For example, Japanese Patent Kohyo No. 500169/1981 discloses a process involving the use of an apparatus in which the upper feed roll of a pair of feed rolls is located slightly ahead of the lower one. The strands are passed through the two rolls to a support having at the top thereof a fixed blade and cut into pellets. This apparatus, however, cannot cut flexible strands into uniform pellets.
Where a multiplicity of flexible strands are cut with a conventional strand cutter, the strands may be introduced by hand one by one between upper and lower feed rolls. In this case, it is necessary to bring the hands in close proximity to the feed rolls because of the flexibility of the strands. As a result, there is a risk of pinching the hands. Furthermore, a considerably long time is required to complete the introduction. In particular, in the case where at least one hundred strands are introduced by hand, strand loss is quite high during the time it takes to introduce the strands, which is not preferred. On the other hand, attempting to introduce the strands in a bundle results in twisting of the bundle caused by overlapping strands before the bundle reaches the feed rolls. This in turn disturbs the feed of the strands and results in obliquely cut pellets or pellets having an uneven cut length.
Even if many strands could be introduced into the feed rolls while being laid in parallel, the strands will, because of their flexibility, vigorously vibrate vertically and horizontally between the feed rolls and the rotary blade owing to impact, repulsion or the like at each cutting to give pellets obliquely cut or having an extremely uneven cut length. Use of the thus-obtained obliquely cut or uneven pellet in extrusion results in fluctuations in the amount charged to the extruder, fluctuations in load of the extruder or the like, thereby rendering it difficult to consistently obtain uniform molded articles.